Is it possible to remove the clutch cover engine casing without draining the oil, as this is a hassle..
Also i need to replace the gasket and have never done it before, any tips ?
No, it is not possible to remove this cover without draining the oil, it is where all the oil is held. As for gaskets, they really are not hard at all, just make sure to carefully remove all traces of the the old gasket, I scrape by hand with a razor blade, and don't let your new gasket get damaged. You can run a little line of oil or grease with your finger when positioning the gasket to help set it in the right position, then I try to use the cross bolt tightening pattern starting from the center out so the gasket is sure to lay correctly. Just did this last month, engine is now full of oil with no leaks.
This is the absolute best thing in the world for removing gaskets:
(http://hi.atgimg.com/img/i/6416/3673-7732.jpg)
When you remove the sidecover bolts you'll do so in a sequence, rather than just taking each one out individually. You want the pressure to be released evenly, otherwise you might snap a bolt.
Be careful, the some of the gaskets on the motor have asbestos in them - the side cover gasket is one of them.
What you can do to make installation easier, and to ensure that everything seals nicely, is apply a thin coat of regular, NEW motor oil on both sides of the gasket as well as both mating surfaces.
When you re-install the cover please be sure to tighten the bolts evenly. You may wish to apply some non-permanent thread locker or some type of soft silicone sealant to help keep the bolts in place.
You can replace that gasket without draining the oil if you lean the bike over so the oil drains to the opposite side of the engine. Just put a pillow or blanket between the bike and whatever you lean it against (porch post or tree works well) so it doesn't get scraped. If the gasket sticks to the cover you can use a wiz wheel or gasket remover spray on it. Don't use them on the engine side, may contaminate the oil and bearings.
-Jessie
(http://www.asianiron.com/media/catalog/product/cache/3/image/5e06319eda06f020e43594a9c230972d/A/0/A0800210-Gasket-Remover.jpg)
Its a good excuse for an oil change. If you just did one recently, you could drain the oil into a clean container and then put it back in the bike when you are done.
In addition to the big gasket, you may also want to replace the seal under the rotor cover that goes around the rotor's shaft.